1. Field of the Invention
The present invention relates to an apparatus and a program for evaluating digital photographic images.
2. Description of the Related Art
Processing of subjects pictured in digital photographic images, by operators extracting the subjects, such as humans, from within displayed digital photographic images by using a mouse or the like, is being performed. However, in the case that processing is performed while tracing the subjects within the digital photographic images with a pointing device, the burden on the operators is great. In addition, the skill in tracing varies for each operator, and uniform finished cannot be obtained.
With the recent spread of digital still cameras, there is demand to administer image processes on digital images to obtain desired finishes. Administering different image processes on a pictured subject and a background, to cause the subject to stand out, is an example of such an image process. To meet this demand, systems have been proposed, in which main portions and backgrounds of images are automatically separated, and the backgrounds are blurred in order to emphasize the main portions, without an operator having to perform the troublesome task of specifying boundaries between the main portions and the backgrounds. Specifically, an image is divided into regions such that adjacent pixels having differences in data less than or equal to a threshold value are included in the same region. Then, features of each region are calculated, and whether the divided regions are background regions or main portion regions is estimated, based on the features. Thereafter, the main portion is emphasized, by blurring just the background region, or by blurring regions other than the main portion regions (refer to Japanese Unexamined Patent Publication No. 2001-057630, for example).
Other systems has been proposed, in which cells within images that include pixels having edge intensities greater than a predetermined threshold are extracted as edge cells, continuous regions which are collections of the edge cells are generated, and the cells positioned outside the periphery of the continuous regions are extracted as outline cells (refer to Japanese Unexamined Patent Publication No. 2002-236929, for example).
However, the system disclosed in Japanese Unexamined Patent Publication No. 2001-057630 judges regions outside a mask (circles or ovals having an image at its center) as background regions, and extracts the boundaries of main portions assuming that the main portions are present within the mask. Therefore, the system is not capable of dealing with varied images.
In addition, in the case that a photographic image is viewed by a human, clothes worn by subjects can easily be recognized as clothing. However, there are clothes of various textures, and therefore, edges detected by a system such as that disclosed in Japanese Unexamined Patent Publication No. 2002-236929 may include those formed by textures. Accordingly, this system cannot extract always exact outlines.